The casting of thin metal filaments developed from a metal extraction process includes a container of molten metal and a rotating disk with a sharp pointed periphery which is lowered into the melt. As the periphery of the disk passes through the molten metal a certain portion of the metal adheres to the cooler metal disk to form a filament or wire. When the disk emerges from the molten material the mass adhered to the disk periphery freezes and as a result contracts in volume, thereby squeezing itself off of the periphery of the disk and separating as a wire product.
Later development involved feeding the rotating disk by gravity from a tundish supported above the horizontal axis of the casting surface.
Relatively recently techniques have been developed for casting thin but wide strips of metal by this technique using a rotating casting surface in the form of a drum or cylinder. The main problem has been defects in the cast strip. Unfortunately the defects create a non-uniform product because the kinds of defects are not predictably located. Various theories have been advanced as to why there is no uniformity in the cast strip but it is believed to be generally accepted that much of the problem stems from differential cooling rates in the solidifying metal.
A partial solution to that particular problem has been suggested and is generally accepted, namely, providing circumferential grooves around the cylindrical casting surface. It is important that the grooves be relatively shallow and numerous, for example, the depth recommended is about 0.025-0.25 millimeters. It is also recommended that there by from eight to thirty-five grooves per centimeter across the surface of the casting drum. This is described in International Patent Publication No. WO87/02284 and to the extent necessary for an understanding of this invention said publication is incorporated herein by reference.
It will be noted in said International Patent Publication that it is desirable to condition the surface of the rotating casting drum at a location between the place where the cast strip separates from the casting surface and where the casting surface again encounters the molten metal discharged by the tundish. The publication suggests wiping the casting surface with cloth or a horsehair brush.
Unfortunately, the use of such surface conditioning apparatus is inadequate because a certain portion of the molten metal will have adhered to the casting surface and dust and debris from the factory environment and the flakes of metal not separating from the casting surface tend to create heat transfer differentials in the metal strip drawn from the melt.
There is a need for greater efficiency in removing dust, debris and melt residue from the casting surface prior to the time it re-enters the melt.